On Mon 20-08-18 11:03:53, Andi Kleen wrote: > On Mon, Aug 20, 2018 at 06:29:38PM +0200, Michal Hocko wrote: > > On Fri 17-08-18 15:27:33, Guenter Roeck wrote: > > > Hi, > > > > > > the following crash is seen in v4.4.148, v4.4.149, v4.9.120, and v4.9.121 > > > with CONFIG_TRANSPARENT_HUGEPAGE=y, CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y. > > > > Could you try to apply fd7e315988b7 ("x86/mm: Simplify p[g4um]d_page() > > macros"). I do not see it in stable 4.4 tree and it has been introduced > > much later in 4.14. This one gave us quite some headache because it is > > soooo easy to overlook. > > Good catch! > > I tested that with 4.9 and backporting the patch indeed fixes the > syzcaller test case running in a KVM VM. Backported patch appended. > > Should probably go into 4.4 and 4.9. > > Cannot explain the 4.17 report unfortunately.
I haven't seen that one yet and likely won't get to it tomorrow as well but I would start looking for a direct pte_val usage. We have had som out of tree xen code which was doing exactly this. Not really easy to find by a code inspection. -- Michal Hocko SUSE Labs